Network Foundation Cisco Routing switch Three

Hot Backup Routing protocol Hsrp:cisco Private protocol

Ensures that when the network edge device or access link fails, the user communication can be quickly and transparently restored to provide redundancy for the IP network, by using the consent virtual IP address and virtual MAC address, two or more routers on the LAN segment can be used as a virtual router for external services.

HSRP enables Cisco routers within a group to monitor each other's running state.

HSRP Group Members:

Active routers

Backup router

Virtual routers (gateways on a LAN)

Other routers

HSRP Virtual MAC address format

0000.0c07.ac2f

Vendor code: HSRP Virtual MAC address, HSRP encoding always 07.ac

HSRP message

All routers in HSRP send or receive HSRP messages

UDP port Number 1985

Send HSRP messages using group advertisement, multicast address 224.0.0.2

Ttl=1

HSRP Status and Timers

HSRP Status:

Initial state

Learning Status

Listening status

Statement status

Backup Status

Active state

HSRP Timers

Hello interval (default 3s)

Hold Time (default 10s)

To configure an HSRP member:

Router (config) #interface fastethernet 0/0 (Gateway interface into the router)

Router (config-if) #standby 1 track F0/1 (tracking router port 1th)

Router (config-if) #standby 1 IP virtual gateway IP

Router (config-if) #standby 1 priority 195 (configure HSRP precedence, priority range 0-255, default = 100)

Router (config-if) #standby 1 preempt Configure preemptive rights

Router#show Standby Brief (view HSRP summary to see if it is a backup or active router)

HSRP Port Tracking:

Router (config) #interface fastethernet 0/0 (enter Gateway Port)

Router (config-if) #standby 1 track F0/1 (tracking router port 1th)

Router (config) #interface fastethernet 0/0 (Gateway port for access to the backup router)

Router (config-if) #standby 1 priority 195 (configure HSRP precedence, priority range 0-255, default = 100)

Router (config-if) #standby 1 preempt Configure preemptive rights

The generation of broadcast storms:

How the switch works: forwards the data frame according to the MAC Address table if the address is unknown. Broadcast, if the switch receives a broadcast frame, it is also sent to all ports

A broadcast storm occurs when there is a physical loop in the network.

STP protocol (Spanning Tree Protocol)

Logically disconnecting loops, preventing broadcast storms from generating when line failure, blocking interfaces are activated, resuming communications, and the role of backup lines

Algorithm:

Select the root bridge (Rootbridge) for each broadcast domain

Select root port (root Ports) for each non-root bridge

Select the specified port (dseignated Ports) on each network segment

Non-specified port, non-root port blocked

Select the root bridge

Bridge ID

The bridge ID is unique, choosing the switch with the lowest bid value between the switches as the root bridge in the network (bridge ID8 byte value range: 1-65535)

Default value: 32768

Select the root port

Select Root port based on: lowest root path cost to root bridge, direct connected Bridge ID minimum

Root path cost: The sum of the cost of all links on the path of the bridge with the root bridge

The relationship between bandwidth and path cost: (The higher the bandwidth, the lower the cost)

Link bandwidth (Mbps) path cost

10 100

16 62

45 39

100 19

155 14

622 6

1000 4

Select the specified port

The ports on the root bridge are all specified ports, and on each network segment, select a specified port.

Specify the port selection order on the non-root bridge:

The root path cost is lower > The value of the bridge ID of the switch is minimal > The value of the port ID is minimal.

Finally, a logical structure without loop topology is formed.

BPDU Bridge Protocol Data unit:

BPDUs send BPDUs using group advertisements.

There are two types of BPDUs:

Configure BPDUs.

Topology Change channel (TCN) BPDUs.

The BPDU text segment.

BPDU Bridge Protocol Data unit:

The BPDUs contain the keywords:

Field byte function

Root Bridge ID 8 is used to advertise the ID of the root bridge

Root Path cost 4 shows how far this BPDU is from the root, and how much it costs

Send Bridge ID 8 sends the ID of this BPDU bridge

Port ID 2 The ID of the port that delivered the paper

When the switch is started, assume that you are the root bridge and fill in the Root Bridge ID field in the outgoing BPDU with its own bridge ID.

When receiving bpdus from another switch, compare the bridge ID, select the smaller one to add to the root bridge ID,

When all the switches in the network receive all the BPDUs and compare them, you can choose the only one root bridge

Convergence of STP

5 STP states for switch ports

Status use

Forwarding (Forwarding) sending/receiving user data

Learning (learning) Building Bridge tables

Listen (Listening) build an ' active ' topology

Blocking (Blocking) receives only BPDUs

Disable (Disabled) Force shutdown

3 Types of Timers for STP

Hello time: The time interval between network Bridge send configuration BPDU messages, default 2 seconds.

Forwarding delay: The time interval that a port spends listening to learning state, default 15 seconds

Maximum aging time: the maximum time that the switch stores a BPDU message before it drops it, by default 20 seconds

The relationship between VLANs and STP:

pvst+ (enhanced per-vlan spanning tree)

pvsta+ Configuration Meaning: Configure the network in a relatively stable switch for the root bridge, the use of pvst+ to achieve Network load sharing

Configuration commands for pvst+

To view the configuration of the spanning tree:

Switch#show spanning-tree VLAN 1

Switch (config) #spanning-tree VLAN 1 Prio priority Value {Note: Priority is worth a multiple of 4096 (that is, the switch with good performance as the Root Bridge)}

Switch (config) #spanning-tree vlan 1 root primary can be used without a value to specify root directly

Switch (config) #spanning-tree vlan 1 root secondary (backup bridge tree, configure standby on another three-layer switch)

(Backup switch to create VLAN and configure trunk for all switches, note: Layer three switch must first package and configure trunk)

Network Foundation Cisco Routing switch Three